code: def get_address(self):
      return self.address
  
imports: import grpc
  import os
  import time
  import threading
  from concurrent import futures
  from parl.remote import remote_constants
  from parl.remote.grpc_heartbeat import heartbeat_pb2
  from parl.remote.grpc_heartbeat import heartbeat_pb2_grpc
  from parl.utils import logger, get_ip_address
  import psutil
  import multiprocessing
label_desc: Use image node_id 2 for calling the HeartbeatServerThread obj's underlying member method code with example usage: obj.get_address() and returns: self